Gliederung

Background and aim: Multimorbidity, accompanied by polypharmacy, is an increasing problem in primary care, especially in elderly patients. Multiple chronic conditions and their pharmacological treatment increase the risk of interference between drugs and diseases and thus of inappropriate prescribing. Additionally, contradictory therapeutic goals for different conditions may complicate clinical decision making, making individual risk-benefit-estimations (i.e. prioritizations) necessary to meet patients’ needs. We aimed to determine the prevalence of inappropriate prescribing resulting from a lack of consideration for contraindications in elderly multimorbid patients in primary care and to assess the inter-rater agreement in this process.

Material and method: Cross-sectional study in 20 general practices (GP) each with randomly selected patient IDs from a list of the 50 most cost-intensive patients/practice generated by the practice software and checked for potential eligibility (≥ 65 ys, ≥ 3 chronic conditions, ≥ 5 drugs continuously taken, ability to participate in a telephone interview) by the GP. After obtaining informed consent up to 10 patients/practice were included. Data source was the GP documentation. The first step of identifying drug-disease interaction risks (‘Gegenanzeigen’) was performed by an electronic database tool which connects each drug (ATC-code) with contraindications (according the summary of medicinal product characteristics as digested in Rote ListeÂ® coded as three-digit ICD-10). All potential drug-disease interactions (DDI) identified by this tool were reviewed by two independent investigators (both pharmacists), and discrepancies were reviewed by rater C (experienced general internist).

Results: From 18 GP practices 169 patients were included: 84 were male (49.7%), with a median age of 74 (range: 65 to 97), and a median of 15 diagnoses/patient (5 to 33). In total N=1,471 prescriptions were documented by GPs (8.7 per patient; 5 to 16). 260 potential DDI were identified by the electronic tool. Rater A considered 29/260, rater B 37/260 to be clinically relevant DDI (agreement 81% , with 202/8 prescriptions rated as appropriate/inappropriate by both raters and 50 discrepancies in rating (kappa=0.134)). After the final rating (rater C) the prevalence of DDI was 1.97% of prescriptions (29/1,471) in 14.8% of patients (25/169; range: 0 to 2 per patient). DDI were seen in 61% of GPs (11/18; 0 to 4 per practice) and in 15/157 five-digit ATC-groups. DDI most often involved selective beta-blockers (8/29), which were the most frequently prescribed drugs in the cohort (6.3% of all prescriptions, 93/1,471), resulting in a relative DDI frequency of 8.6% (8/93). In two groups of NSAIDs (acetic and propionate acid derivatives) almost every fifth prescription took no account of contraindications and almost 10% of prescriptions for oral anti-diabetics, sulfonyl urea derivatives, systemic glucocorticoids, and prokinetics ignored DDI.

Conclusion: The extent of potentially inappropriate prescriptions due to disregard of DDI risks in primary care, especially in multimorbid patients, is remarkable. Differences in rating might reflect the difficulty in prioritization in this patient group with its partly contradictory therapeutic goals.